Multimedia PCs often incorporate CD-ROM drives and audio subsections. CD-ROM players are valuable as data storage devices, but also may be used to play standard Audio CD disks. However, typical computers today require that the CPU be fully xe2x80x9conxe2x80x9d to play an audio CD. As a result, a typical portable computer today can only play CDs for about 2-3 hours.
Operation of the Portable CD-ROM and Audio Subsection Today
Portable computers today are typically organized as a system including a Microprocessor and its support chips, as well as common peripherals (including, e.g., the graphics subsection, PCMCIA controller, hard disk and floppy disk controller, interface port control, such as for printer and serial busses, for example, keyboard controller, etc.) which interface to the CPU. A fixed disk drive and CD-ROM are typically attached on a common bus, such as an IDE or SCSI bus. xe2x80x9cATAPI-compliantxe2x80x9d CD-ROMs are capable of either data retrieval, or playing audio disks (so called xe2x80x9cRedbookxe2x80x9d or xe2x80x9cCD-Axe2x80x9d disks). The CD-ROM control signals and data come over the common bus, but audio signals are output directly from the CD-ROM on an independent analog output.
A typical example of a computer audio system employs an audio mixer or xe2x80x9cSoundBlasterxe2x80x9d compatible audio codec. The output of the CD-ROM is a common input to the Audio Mixer. The function of the mixer is to provide volume control of the CD-ROM outputs along with other PC sounds. The output of the mixer goes to a power amplifier, which outputs to speakers or to a headphone jack. The audio codec and power amplifier together form the Audio section of the computer.
A Real Time Clock (RTC) is a virtually universal peripheral to today""s PCs. The RTC is always powered up, and is used to both keep track of the time and date and to act as an xe2x80x9calarm clockxe2x80x9d to the system, whereby the system may be xe2x80x9cwokenxe2x80x9d from Suspend after a predetermined time has passed.
Power management circuitry is an integral part of a typical battery-powered computer. Power management is principally controlled by a program in the CPU memory and enables active status to the peripherals and support logic of the system.
Typically, a low-power xe2x80x9cSuspendxe2x80x9d mode is supported, where the entire state of the system is frozen, timing clocks are turned off, and power is removed from any logic whose state is unimportant. Power to at least some portions of the system must remain active during Suspend. The function of Suspend mode is to freeze the condition of the system while taking the least amount of power. In Suspend, the only activity the system supports is to recognize a xe2x80x9cwakeupxe2x80x9d event and return to normal operation: the xe2x80x9cRESUMExe2x80x9d sequence may be initiated by the system (e.g. by button press, modem ring, Real time clock alarm, or low battery event).
Typical power dissipation for the unit in a FULL SUSPEND mode is about 200 milliwatts. After xe2x80x9cResumexe2x80x9d from Suspend, power to all devices is returned, and the pre-existing states of the CPU, the operating system, and the application is restored to its state before Suspend was executed.
Suspend mode is usually entered after a period of inactivity, after a critical condition event (for instance, a low battery condition or overtemperature of the unit), or manually by the user.
Typically, when in Suspend mode, power to the fixed disk and CD-ROM drives are disconnected (shown here as SW1 under the control of a SUSPEND status signal). The audio subsection is also placed into a non-functional mode; either power may be removed completely from the system or the Audio mixer/Codec and power amplifier may be placed into a non-functional SUSPEND mode under the control of the SUSPEND status line.
The peripheral components are also placed into inactive functionality or turned off by the single SUSPEND status.
Applications run within the CPU to play an audio CD. For example, within the Windows operating system, these utilities are called xe2x80x9cMedia Playerxe2x80x9d or xe2x80x9cCD player,xe2x80x9d though many such applications are known.
Limitation of Known Implementations
For the sole purpose of playing an Audio CD, today""s portable computer uses more power than is required. This is because, in order to play an Audio Compact Disk today, the entire peripheral set remains powered and functional, although they are not being used. Since a full SUSPEND globally powers down all peripherals, it is not possible on today""s portable computers to allow the system to suspend all unnecessary system elements while playing an audio CD.
Innovative System and Method for Low-Power CD Audio
The present application describes a computer system and method which provides a xe2x80x9cCD-player Suspendxe2x80x9d mode, where the audio section and CD-ROM are left active while the remaining system is placed into a low power mode.